Electrodes which can be of large planar shape and be formed of metal mesh often have an electrocatalytic coating which will suffer diminished electrocatalytic activity over a greatly extended use. These electrodes, thus, have to be refurbished for reuse. It has been known in such refurbishing, where such large planar mesh electrodes are secured to a riser and form part of an electrode assembly, to use at least a part of the electrode in the refurbishing. Thus, it is taught for example in U.S. Pat. No. 3,940,328 that such a previously used electrode may form a base to which a fresh electrode is secured. The old mesh electrode, which is adhered such as by welding to the riser, can be substantially cut away, nevertheless leaving a portion of the old electrode, which is secured to the riser, in place. Then a new electrode, which may be in envelope form, is slipped over the riser plus old portion of the mesh electrode. The new electrode can conform to the working faces of the old electrode.
The old planar electrode members may form more than a simple base for the new electrode members. In U.S. Pat. No. 4,154,667 it is taught that the old electrode member secured to a riser may be substantially cut away. This can leave electrode sections which are closest to the riser and bonded to the riser. By a forming operation, these sections may be made into spring-like members. The new electrode planar members are then secured to these spring-like members. Such a technique can be used for converting box form electrodes to expandable form electrodes.
Electrode assemblies other than for diaphragm cells include assemblies utilized in filter press electrolyzers. Such assemblies for these electrolyzers can have a mesh electrode which is separated by standoffs from a back pan. For example in U.S. Pat. No. 4,923,582, there are taught such electrode assemblies, which assemblies have spring members between back pans and electrode members. The assemblies are also subject to eventual diminishing of electrocatalytic coating activity for the electrodes. Thus, refurbishing these assemblies is necessary.
Since the electrodes can be welded to the members separating the electrodes from the back pans, which separating members are also usually welded to the back pans, refurbishing by replacement of the electrode members can be a problem. In removing the electrode from the back pan or from the standoff, it has been known to mechanically tear the electrode, e.g., an electrode in mesh form, away from the top of the standoff. However, where the electrode mesh is most secure to the standoff, e.g., at weld nuggets, these portions of the electrode mesh must be removed by further operation, such as grinding. This can very deleteriously effect the dimensions of the top of the standoff. To regain these dimensions, further operations such as punching must be utilized. The overall operation can be very labor intensive and thus uneconomical.
It would be desirable to be able to refurbish such assemblies efficiently and economically. This would not only be economy of refurbishing at the site of use of the assembly, e.g., an electrochemical plant, but also the economy of refurbishing the assembly without substantial destruction and thus substantial reconstruction of the assembly.